That makes sense but why not remove the DOH for IDPA?
Well, if you're talking about using the same holster for both IDPA and USPSA, it would be a PITA to switch back and forth. For instance, my USPSA rigs are mounted on double belts and I wouldnt care to remove them often. When I used a Bladetech, it needed to be secured with zip ties. Double belts arent allowed in IDPA, so my holsters are set up for a Wilderness belt. If you're not using a DOH setup, you may just prefer something other than a Bladetech.
Strictly my opinion, but for an 'on the belt' non-DOH, competition Kydex type holster, the Comp Tac and KyTac holsters are a bit nicer for about the same $, and the Safariland is good too, for much less $. So for the IDPA-only guys,the Bladetech is just one of many choices.
I could talk about holsters all night, but I'll keep it short;-)
I rarely shoot IDPA, but when I do, I use a Safariland.
For USPSA there arent many DOH choices (not for a CZ anyway) and I personally didnt care for the Bladetech. (I own and have have owned a lot of Bladetech stuff, its good stuff, this is not a criticism of them at all)
KyTac made me an awesome owb holster, but I really wanted a DOH style. So, Rick Edwards at Performance Holsters made me one. His DOH design rocks, it isnt a convertible like the Bladetech, but it's nicer, and is also a bit nicer than the Ready Tactical.
YMMV.